There are many applications for chip cards in the modem world, for instance as phone cards, ATM cards, access cards for Pay-TV and so-called “subscriber identity modules” or SIM cards for short. In order to produce the cards as cost-effectively as possible, a uniform size of 85×54 mm, i.e. the format of a credit card, was agreed. This ensures the easy handling of said cards. At the beginning of the GSM era, in the early nineties, even SIM cards were used in this format. As a result of increasing miniaturization, however, today's SIM cards are only a fraction of the original size.
SIM cards are nevertheless produced using the same process as in the early nineties. In this process, a comparably small chip card module of the approximate size of the contact field, which is standardized in accordance with ISO 7810, is installed into a carrier 85×54 mm in size. One possible method is based on bonding the chip card module into a milled recess in the chip card. Another possible method is based on placing the chip card module into the mold when molding a card and installing it into the carrier in this way.
Today's small SIM card is then punched out of the carrier, or a perforation is produced to enable the SIM card to be removed from the carrier. Prior to this process, the SIM module may be personalized, i.e. given a unique electronic code which will later permit the positive identification of a subscriber to a telephone network. The SIM card is only ready for insertion into a holder in a mobile phone after being punched or broken out of the carrier.
Devices for use with a chip card, such as mobile phones, are provided with holders with device contacts and a, press-on device for this purpose. If the chip card is inserted into the holder, the press-on device ensures a reliable contact between the planar contact field of the chip card and the device contacts.
Owing to the design of commonly used press-on devices, the thickness of the chip card plays an important role, because only a defined thickness allows the insertion of the chip card into the holder on the one hand while ensuring the required contact force on the other hand. The press-on device, which applies pressure to the top of the chip card, is elastically deformed. when the latter is inserted and introduces a greater or lesser degree of force into the chip card, depending on its thickness. A thicker chip card results in a higher pressure and therefore contact force, a thinner chip card in a lower pressure and therefore contact force. Additional spring-loaded contacts are often used, which, owing to a relatively low spring constant, are better able to compensate for component tolerances.
An example for a press-on device are guide rails under which the card is inserted. These guide rails allow the chip card to move in the direction of insertion while preventing any movement in the transverse direction. When the chip card is inserted into the holder provided with spring-loaded contacts, the chip card pushes these contacts away, pressing the contact field against the device contacts as a result of its spring-constant.
Further examples for press-on devices are flaps pressed against the top of the chip card or latching devices preventing the opposite movement of the chip card during insertion from a defined position in the direction of insertion, which may extend at right angles to the surface represented by the contact field.
For the reasons explained above, holders in common use are designed for the thickness of a credit card of approximately 0.8 mm. Conversely, this means that a chip card has to have this thickness if it is to function satisfactorily. This is achieved, as mentioned above, by installing the chip card module into a card carrier, which can be produced to very fine tolerances. The chip card module has to be correspondingly thinner, having a thickness of approximately 0.6 mm.
Quite apart from polluting the environment with unnecessary waste, the conventional production method is technically complex and therefore expensive because of the many process steps involved. In addition, the volume available for the chip is extremely limited as a result of this technology. The production of the chip either requires an expensive method allowing for small structures, or functionality has to be sacrificed. In either case, conditions for producing chip cards are less than satisfactory.